1. Field of the Invention
The present invention relates to a transmission control method for uplink user data in a mobile communication system in which a plurality of HARQ processes are applied to the uplink user data to be transmitted from a mobile station to a radio base station, and a mobile station, a radio base station, and a radio network controller used in the transmission control method.
2. Description of the Related Art
In a conventional mobile communication system, when setting a Dedicated Physical Channel (DPCH) between a mobile station UE and a radio base station Node B, a radio network controller RNC is configured to determine a transmission rate of uplink user data, in consideration of hardware resources for receiving of the radio base station Node B (hereinafter, hardware resource), a radio resource in an uplink (an interference volume in an uplink), a transmission power of the mobile station UE, a transmission processing performance of the mobile station UE, a transmission rate required for an upper application, or the like, and to notify the determined transmission rate of the uplink user data by a message of a layer-3 (Radio Resource Control Layer) to both of the mobile station US and the radio base station Node B.
Here, the radio network controller RNC is provided at an upper level of the radio base station Node B, and is an apparatus configured to control the radio base station Node B and the mobile station UE.
In general, data communications often cause burst traffic compared with voice communications or TV communications. Therefore, it is preferable that a transmission rate of a channel used for the data communications is changed fast.
However, as shown in FIG. 1, the radio network controller RNC integrally controls a plurality of radio base stations Node B in general. Therefore, in the conventional mobile communication system, there has been a problem that it is difficult to perform fast control for changing of the transmission rate of uplink user data (for example, per approximately 1 through 100 ms), due to the increase of processing load and processing delay in the radio network controller RNC.
In addition, in the conventional mobile communication system, there has been also a problem that costs for implementing an apparatus and for operating a network are substantially increased even if the fast control for changing of the transmission rate of the uplink user data can be performed.
Therefore, in the conventional mobile communication system, control for changing of the transmission rate of the uplink user data is generally performed on the order from a few hundred ms to a few seconds.
Accordingly, in the conventional mobile communication system, when burst data transmission is performed as shown in FIG. 2A, the data are transmitted by accepting low-speed, high-delay, and low-transmission efficiency as shown in FIG. 2B, or, as shown in FIG. 2C, by reserving radio resources for high-speed communications to accept that radio bandwidth resources in an unoccupied state and hardware resources in the radio base station Node B are wasted.
It should be noted that both of the above-described radio bandwidth resources and hardware resources are applied to the vertical radio resources in FIGS. 2B and 2C.
Therefore, the 3rd Generation Partnership Project (3GPP) and the 3rd Generation Partnership Project 2 (3GPP2), which are international standardization organizations of the third generation mobile communication system, have discussed a method for controlling radio resources at high speed in a layer-1 and a media access control (MAC) sub-layer (a layer-2) between the radio base station Node B and the mobile station UE, so as to utilize the uplink radio resources effectively. Such discussions or discussed functions will be hereinafter referred to as “Enhanced Uplink (EUL)”.
In the mobile communication system to which the “Enhanced Uplink” is applied, either of a scheduled transmission or a non-scheduled transmission is performed.
In the scheduled transmission, each of upper layer flow will be transmitted, based on the transmission allocation by the radio base station Node B.
In the non-scheduled transmission, each of upper layer flow will be transmitted automatically without following the transmission allocation by the radio base station Node B.
Against the general upper layer flow (uplink user data), the scheduled transmission is performed.
On the other hand, against the upper layer flow which has the strict requirements regarding the transmission delay, such as voice information, control information, or the like, the non-scheduled transmission is performed.
However, in the non-scheduled transmission, it is required to reserve hardware resources in advance. Accordingly, the unnecessary non-scheduled transmission will cause a waste of hardware resources.
In addition, in the mobile communication system to which the conventional “Enhanced Uplink” is applied, a “non-scheduled transmission reserved process” and a “non-scheduled transmission limited process” are existed as a HARQ process.
In the “non-scheduled transmission reserved process”, it is configured that only the non-scheduled transmission can be performed.
In the “non-scheduled transmission limited process”, it is configured that the non-scheduled transmission will not be performed in all HARQ processes other than the HARQ process to which the “non-scheduled transmission limited process” is applied.
Referring to FIG. 3, an example when the process #1 and the process #2 are set as the “non-scheduled transmission reserved process” in the HARQ having 6 processes.
In the above case, as shown in FIG. 3, the non-scheduled transmission can be performed in every process. However, the scheduled transmission can be performed in the process #3 to the process #6 only.
As a result, the radio base station Node B can control a transmission rate of the scheduled transmission less than an absolute transmission rate of uplink user data, which is notified by using an “Enhanced Absolute Grant Channel (E-AGCH)”, and the like.
Accordingly, the radio base station Node B can make the mobile station UE to transmit the uplink user data using the transmission rate of the scheduled transmission which differs per the mobile station UE, so that the radio base station Node B can allocate the appropriate transmission rate of the uplink user data to each mobile station UE, even when the radio base station Node B signals the absolute transmission rate of the uplink user data which is common to each mobile station UE.
Referring to FIG. 4, an example when the process #1 and the process #2 are set as the “non-scheduled transmission limited process” in the HARQ having 6 processes.
In the above case, as shown in FIG. 4, the non-scheduled transmission can be performed in the process #1 and the process #2 only.
As a result, the radio base station Node B has to prepare the hardware resources for reception in the process #1 and the process #2, in which the non-scheduled transmission will be performed, only. Therefore, hardware resources can be used effectively.
As described above, in the mobile communication system to which the conventional “Enhanced Uplink” is applied, it is possible to set the transmission rate of the scheduled transmission in each mobile station UE appropriately, by using the “non-scheduled transmission reserved process” as HARQ process.
In the meanwhile, in the mobile communication system to which the conventional “Enhanced Uplink” is applied, it is possible to decrease the amount of hardware resources for reception to be prepared for the non-scheduled transmission, by using the “non-scheduled transmission limited process” as HARQ process.
However, in the mobile communication system to which the conventional “Enhanced Uplink” is applied, there has been a problem that it is not possible to simultaneously set the transmission rate of the scheduled transmission appropriately and decrease hardware resources for reception in the non-scheduled transmission.